We have studied the mechanism of the mechanochemical interaction between Na2CO3 and Nb2O5 in the initial stage of milling, before the final crystalline oxide product, i.e., NaNbO3, is formed. In order to do this, the milling parameters were chosen to give a relatively low ball-impact energy. In addition, one of the reactants, i.e., Na2CO3, was milled also individually so that the mechanochemical effect on the separately milled compound could be determined. X-ray diffraction analysis, thermal analysis and infrared spectroscopy were used in order to characterize the samples after different milling times. The mechanochemical treatment of the Na2CO3-Nb2O5 mixture results in the formation of a carbonato complex, which represents an intermediate stage in the mechanochemical synthesis of NaNbO3. (c) 2006 Elsevier B.V. All rights reserved.